Electric remote indication system



April 16, 1946. E. A. H. BOWSHER ELECTRIC REMOTE INDICATION SYSTEM Filed Nov. 24, 1942 INVENTOR EDWARD A. H. BOWSHER ATTORNEY Patented Apr. 16, 1946 UNITED STATES PATENT g;

I innor no REMOTE mmoa'r oN e ;EdwardAlhertjHenryjBowslier,

- I England, assignorito-lnternational Standard n 1 -?i re en wiierh. n he; l j Application November 24, 1'942;Serial-No.466,816 i ""In Great liritainM-arclifi, 194? flfi clalnisc (o1. mi-'35s) This invention relates to electric signalling systems; and more particularly though not'exclusively to systems fortheremote control and/or supervision of electrical power supply netwdrks.

In such remote controlflsystems', "the'sign'allin'g between a central control station and various sub-stations or oiiices is generally carried out by means of D. C. impulsingbn a pairof pilotwires. Where the number of sub-stations is largeand where they cover a conside'rable' area, it is sometimes necessary to employ tandem working "in order to achieve economy of pilot wires. In large multi-ofiice areas, there are many pairs of offices located several miles apart between-which there is comparatively little traflic. Instead or providing the expensive network of direct trunk groups between each combination of such dffices, each 7 oflice in the area has lgroup's of trunks to and from one centrally located oflice known as the tandem oflice. Tandem working implies that there is no permanent direct metallicconnection between the central station and the varioussubstations. Radiating f rom the central 'controlst'ation are one or more pairs of pilot wirs'to a series of tandem stations; from'each of which radiate further pairs of pilot wires to the individual substations or ofices. TheB'ritish patent referred to below describes an electric "system for indicating at a central'station of an electrical power distribution network, the condition or'position of apparatus at unattended 'stationsof the network. This electric system is characterized by common supervisory signalingequipment at the central ciated with the same tandem station, access to the 'centra'l station. It is "the object of the present invention to prevent s'uch an occurrence. 4 a The present inVention consists, in an electri circuit arrangement which an equipment is provided for the equipments [on at a time, the commOn 1 equi ment is characterised in; that held to: the exclusive use or oneof -the u'sing {equipments only while I perative, i a dis onsaid using equipment i tinuous manner.-

einvention' wil be e'scribedwithreference to' the accompanying=draw'ing=, which shows; part I of the circuit "arrangements in a tandem station, that a connection established being so devised through tandem can only be held it releases either on disconnection or permanent hold." A, H .l

1 The l drawing shows "in'fld'etail .certain of the circuits at" the tandem 1 intermediate I switching point."*Th"ese circuits and *apparatus cooperate with additional "equipment atFiboth thehcontrol sameness attl' ie substation; as ;will be readily apparentto persons skilled ,in theart. i=5 The central or control 1 station is represented in the drawing by the rectangle Cs which: may

' contain any suitablettypes' of apparatusi-iontrans station'arranged to be connected automatically to any one of a number of different unattended stations connected by independent signer channels to a tandem station whichis co'nne'cted' to the central station, and toi-receive therefrom supervisory signals "characteristicbf the' condi- I ate a second sender at tandein'which then cone I trol s the selection of to the called office and the called station t dial system offices. I i With such a system, as'illustrated for instance the outgoingta'ndem trunk in British Patent 489,000of January 15, 1931; each I tandem station serves a number of sub-stations, and, since the tandem stations areas a rule unattended from a supervisory point of viewjthe possibility arises that 'a fault condition at a substation might permanently hold its 'parent tandem station and so deny other sub'-stations; assocircuits and apparatus sequence; a seizure periodv during which a; source mittijn'g and: receiving signalling-pulses; British Patent 489,000" referred to i above discloses atypical control station of a type suitable for use .in combination with the intermediate station shown in the-drawing."

Only a drawing This line-is representedTby the rectangle it5 andis connected to the number five terminals of the selector switchi oi course; other lines" my be' connecte'd to' the other terminals as may be desiredfi The sub-station line and =station equipment 'represented by: the rectangle #Sinay include eitheruwsing e-sub-station or a plurality of sub"-jstations,}such above-identified British patent. l t, The circuits and apparatus' atxuthe' control stationand 'at'the substations operate in -their usual and normal'manner in "combination with the circuits at the tandem as shown in the drawing so that it is not neces- 'sary to' repeat in detail-'a-Vdescription of these "here." :j i

1 The intermediate switchin'gi-station showngin the drawing is arranged to cooperate with control and sub-'s tations iiof "the type, such as described in the aboveidentified Britishpatent; in which the signals from the "control station ncompriselin common us'e of a plurality 'of single suit-station line is (shown inz tne as disclosedinthe intermediatef points of energy is applied to the transmission line or pilot wires extending to the tandem intermediate station, adigital train of interruptions or pulses line. Thereafter, the sub-station may-return from their normal position to the No. 1 position,

selected sub-station coded signals comprising holds and trains of pulses.

The symbols and in circles-on the-drawing are employed to indicate the positive andnegative terminals of a suitable battery :orrbatteriesxor other suitable source of electrical energy such that current will flow in any completed circuit from any to any symbol.

Upon the seizure by the control stationa source of electrical energy wiIl'be; applied to the pilot wires or conductors extending to the tandem station and cause relay, to -=operate.' Operation of relay IR completes a circuit for the operation of relay B extending from negative potential through thefwinding of relay B, the operated contacts of relay IR to the normal contact of a the ffirst or private bank of-.the sequence orselectorfiswitch, to;;positive potential throughthe firstfselector brush. Thereafter, the circuit at the tandem station-will remain in this condition during the seizure period applied to the conductor .at' the central switching station, as pointed out above. V

At the end of the seizure period a series of pulses, which comprise circuit interruptions, are transmitted from the control station to the intermediate station; The relay-IR at the tandem station followstheserpulses:- Upon the reception of; the first open pulses or circuit interruption relay IR. will release and interrupt the above described circuit atrelayaB. Relay B, however, is slow in releasing,- so that it does not-release at this time. 'Therelease of relay at this time,

in'addition, completes acircuit ,for the operation of relay C-and the sequenceor selector'switch stepping magnet .SS extending from' the positive potential connected-to the No. ,1 brush 0f the selector'switchfthe normal contact of the first banliof the selectorlswitch, the break contacts of relay IR, the inner operated contactsof relay B and lower break contacts of relay-G0, the winding .of relay C and the winding of the selector stepping magnet :83 to negative potential. Both relay C andthe selector stepping magnet operate due to the current flowing through their windings. The operation ofrelay C, completes a circuit for the operationxof: relay'LG extending from negative potential through the winding of relay LG, the operated contacts of-relays C and B to positive potential. The operation of the selector stepping magn'etSS willcause the brush arms of the'selector switch to stepone step either upon the operation of the selector magnetor upon? the release-thereon 1 At theend of the flrstrpulse received from the control station, trelay IR will reoper-ate, reestablish a circuit for holding relay 3 operated and interrupt the circuit through the winding of: relay C and the stepping magnet SS: Relay 0, however, is slow in releasing and will remain operated 'for a short interval of time; "The stepping magnet'SS, however, will at once release.

r When the brushesof the selector sw tch s 3 or relay C and the selector magnet SS.

Thereafter 'upon the reception of each of the succeeding pulses from the control station relay IR will release and again complete a circuit 'throughrelay'fC and the selector stepping magnet SS, thus "tending to maintain relay C operated and ,stepxthe selectorxbrushes an additional step. Duringthe short intervals between the pulses, relay IR is operated and completes the circuit for maintaining relay B operated.

After the final pulse of the first pulse train from the control station is received, relay IR will .reoperate and maintain relay B operated. However, relay IR will not release sufiiciently so as to maintain relay C operated. As a result, relay C releases at this time. The interval between the various trains of pulses, which is sufiiciently long to permit relay C to release, is sometimes v called the interdigital time interval, as pointed out above,.and istransmitted from the control station between each of the trains of pulses, whichpulses usually represent one of the digits. 7

Upon release of relay C in response to the reception of the abovementioned interdigital pause, a circuit iscornpleted for the operation of relay GC extendingv from negative potential through the winding of relay GC, the lower inner operated contacts of relayLG, the break contacts of relay 0 to positive potential through the operated contacts 0f relay B. The operation of relay -(3C extends the transmission path or pilot wires from the control station through its upper operated contacts andthe third and second bank of the selector fir a In the specific arrangement shown in the drawing; it has been' assumed that five pulses. are transmitted in the first train of pulses from the control station; These pulses will cause the selector switch-to step to itsNo. 5 terminal where switch to the selected sub-station the brushes will be resting upon the terminals of the No. 5 sub-station line-extending to one or more of the sub-stations. The operation of relayn Gc described above then completes the transmission path from the controlstation to the sub-station line No. 5. Thereafter, as described above, the control stationwill transmit addi- .tional series or trains of pulses forcontrol equipment associated with the sub-station line No. 5 at any or .all of the sub-stations of that line.

Persons skilled in the art, however, will readily understand that if adifierent number of pulses had been transmitted in the first train, the selectorswitch would have been stepped to a different terminal and thus the-transmission path from the control station extended to a difierent substationline, all under control of the pulses transmitted-from the control station.

- Relay IR follows all of the subsequent pulses transmitted from thecontrol station CS to the sub-station line. When relay I-R is-in itsoperated position, it will complete a circuit for maintaining relay B operated from negative potential through the winding ofrelay B, the operated mg. or relay LG, the lower operated contacts of Bft he terminal' of the first bank upon which the relay GC, the inner operated contacts of relay B,

the break contacts of relayIR, the lower operated contactsof relay LG and theouter operated contacts'of relay B to the first bank terminal upon which brush l is resting and then through brush I topositive potential. Both relays B and LG are sufiiciently' slow in releasing that they are both maintained operated by the current pulse flowing through their winding in the above described circuits due to the operation and release or'reiaym inresponse to received pulses. At the completion of the transmission of pulses from the control station, pulses are sometimes transmitted from the substation to the control station. Relay IR also responds to these pulses and maintains the circuits at the tandem station inthe condition described, thus maintaining the connection between the sub-station line and the control station. The above-identified British patent discloses control stations and sub-stations operating in this manner.

At theend of the communication, that is after the necessary in'formation has been transmitted between the control station and the sub-station, the connection is normally released by removing all sources of energy-from the transmission path both' at the control station and at the sub-station, thereby permitting relay IR to finally release and remain released. Release of relay IRinterrupts thecircuit of relay B as described above. However, upon the long release described above,

relay IRdoes not reoperate to maintain relay B operated. Consequently relay B releases and in' turn interrupts the operating circuits of relays I.

GC and LG. Relays GC' and LG in releasing interrupt thetransmission path extending from the control station to the selected sub-station line and in addition tend to restore the circuits to their original condition. v

The release of relay B in addition completes an auxiliary circuit for returning the selector switch to its normal position. This circuit extends from negative potential through the winding of the stepping magnet SS, the break or selfinterrupting contacts of the selector stepping magnet SS, the outer break contacts of relay B, the terminal on which brushl .ofbank 1 of. the selector switch is resting, to positive potential through the brush No. 1. The stepping magnet SS operates in this circuit and steps the switch and in addition interrupts its own operating circuit; thus'causing it to release. Upon release of the steppin g'magnet SS, its operating circuit is 7 again completed so that it takes another step.

The above cycle of operations is then repeated, advancing the selector switch until the brushes step on to the normal contact, at which time the above described circuit through the winding of the stepping magnet SS is interrupted." The circuit isthen'in condition for seizure from the control station for selectively establishing another connection in the manner described above.

It may sometimes happen that the control station and a' sub-station simultaneously attempt to initiate the transmission of signals in systems of the type disclosed inthe B'ritish patent rereirea from one station mayinterfere with pulses from another and the circuit at the two stations may become blocked so that potential is maintained upon the transmission conductor continuously. In the control circuits of the priorart such conditions tended to tie up the intermediate relay station and prevent its use or operationuntil the trouble is remedied byservice or maintenance attendants. However, inaccordance with the presentinvention, should the transmission path be established between the control station and a sub-station and potential maintained across the transmission path continuously, relay Bwill be maintained operated in the circuit described above. Relay LG is a slow-release relay and it is normally maintained operated by current flow ing through its winding and the break contacts IR during the release periods of the relay IR but will release because the back contacts of relay IR will remain open for too long a period of time. The release of relay LG interrupts the operating orholding. circuits of relays GC andB, which relays thereupon releaseand cause the selector switch to be returned tov normal in the manner the trains or seriesof pulses. -If.the line is maintained open or closed for any appreciable period of time, the connection between the control station and the sub-station line is interrupted and the tandem station restored to its normal condition and available for use in establishing other paths betweenthe control stationand other substation lines. In other words, unless the equipment at both the control station and sub-station line operates satisfactorily in the required manner, the connection between them is interrupted and the switching equipment at the tandem station returned to normal. so that it will be available for establishingother, paths from the control station to othersub-station lines.

Thus, 'just so long, as impulsing or short hold periods continue, relayGC is maintained operated and selector SS. is held on the contact corresponding to the sub-station. If any other condition applies, the connection breaks down automatically. 1

Of courseflthe invention will have other, uses, it could for example, be; used if desired to replace any of the known hold arrangements in a telephone exchange system where equipments such as line-finders and register-controllers are provided for the common use of a plurality, of subscribers one at a time when they wish to set up connections. a

What is claimed is: 1. A signal control system of thetandern type involving main lines extending from a mainstation and extension lines extending :to substations, means for establishing thereover a connection including a switch for selectively; connecting a main line to anumber oi the extension lines,

thereby, enabling transmission ofimpulsesbe 4. A signal control system of the tandem type operated by impulse energization comprising a line circuit, a line switching relay, a line impulse actuated selector inseries with said line circuit,-

a-line'impulse actuated relay having front and back contacts, relay control circuits connected to certain of said contacts, an intermediate con-' trol relay energized-by a circuit including certain others of said contacts, slow releasing relay means connected to be energized under the con trol of contacts of the intermediate control relay and to hold deenergized said line-switchingrelay duringa first code pulse, andto be deenergized and to energize said line switching relay during subsequent code pulses, further slow-releasing relay means controlled by .said first slow-releasing means and controlling said line switching relay to be deenergized only, when said .further slow-releasing means is energized in a discontinuous manner. i

5. A signal control system-of the tandem type for: selectively connecting amain line to a numberof sub-stations comprising a-line-switchin'g re'lay'controlled by an energizing circuit and'controlling said main line, a-selector actuated by line impulses received from said main line, an impulsing relay having front and back contacts, and an additional contactnormally' connected to one 'of said front and back contacts and disconnected shortly after said front and back contacts areconnected, a relay control circuit connected to said front"andback contacts, an intermediate control relay connected to said front and back contacts to control contacts in said energizing circuit, a slow-releasing relay means con nected to said'additional contactto control sec' ond contacts in said'energizing circuit, a further slow-releasing relay means controlled by said first-slow-releasing relay means to control third I contacts in said energizing circuit, said first contacts interru'ptingsaid energizing circuit after an interval substantially exceeding the normal duration of an interpulse period, said second contacts interrupting said energizing circuit during the first code pulse, and said third contacts interrupting said energizing circuit after an interval substantially exceeding the normal duration ofan 'interdigital period;

' 6. A system according to claim 4, in which the selector has an energizing circuit operated by said line-switching relay whensaid line-switching rclay is energized and when, simultaneously, said intermediate control relay is de-energized.

' 7. A system according to claim 5,'in which the selector has an energizingcircuit said line-switching relay when said line-switching relay is energized and when,-simultaneously, said intermediate control relay is de-energized,

8. A system for communicating code pulses operated by from a central station to a number of sub-stations by means of a tandem station comprising a main line for receiving pulses comprising said code pulses, an impulsing relay controlled by the code pulses, distributor means controlled bythe code pulses to connect said main line to 'a selected one of said sub-stations, a -main line switch, relay means controlling said switch, a first slow-releasing relay means controlled by said impulsing relay, a second slow-releasing relay means controlled by the first slow-releasing relay means and controlling therelay means controlling the switch to connect said main line when said second slow-releasing relay means is energized and to disconnect said main line when said second slowreleasing relay means remains de-energized for a time substantially exceeding the normal duration of an interdigital period, said first slow-releasing relay means further controlling contacts in circuit with the relay means for controlling the switch to de-energize it when said first slowreleasing relay means is de-energized for a time substantially exceeding the normal duration of an interpulse period.

j 9; A tandem system for communicating code pulses from a central station to a number of substations, comprising a main line for receiving pulses comprising said code pulses, an impulsing relay controlled by the code pulses, distributor means controlled by the code pulses to connect said main line to a selected one of said sub-stations, a main line switch, relay means for controlling said switch, .a first slow-releasing relay means controlled by said impulsing relay,a second slow-releasing relay means controlled by said first slow-releasing relay means and controlling said relay means for controlling the switch to connect said main line when said second slowreleasing relay means is energized, and to disstrolling said main line connect said main line when said second slowreleasing relay means remains de-energized for a time substantially exceeding the normal durationcf an interdigital period, said firstslow-releasing relay means further controlling contacts in circuit with said second slow-releasing relay means to de-energize said second slow-releasing relay means when said first slow-releasing relay means is de-energi'zed for a time substantially exceedingthe normal duration of an interpulse period.

10. A tandem system for communicating code pulses from a central station to a number of substations, comprising-a main line for receiving pulses comprising said code pulses, an impulsing relay controlled by the code pulses, distributor means controlled by the code pulses to connect said main line to a selected one of said sub-stations, a main line switch, relay means for conswitch, a first slow-releasing relay means controlled by said impulsing relay, a second slow-releasing relay means controlled by said first slow-releasing relay means and controlling said relay means for controlling the switch to connect said main line when said second slow-releasing relay means is energized and to disconnect said main line when said second slow-releasing relay means remains deenergized for a time substantially exceeding the normal duration of an interdigital period, said first slow-releasing relay means further control- 7 ling first and second contacts, said first contacts energize said relay means'and said second-slowreleasing relay means when said first slow-releasing relay means is de-energized for a time substantially exceeding the normal duration of an interpulse period.

11. A system according to claim 8, wherein said first slow-releasing relay means controls an additional slow-releasing relay means operating additional contacts in circuit with said first contacts and so connected as to energize said line switch relay when said additional slow-releasing relay means is de-energized for a time substantially exceeding the size of an interpulse period and to de-energize said second slow-releasing relay means while said distributor means connects said circuit line to a selected sub-station.

12. A system according to claim 8, wherein said distributor means includes a sequence switch having a number of banks of contacts and a wiper for each of said banks, said wipers being arranged to be pulse-driven along said contacts into a number of successive positions, engaging in each position a number of contact means, two of said contact means connecting a selected substation to the circuit line, and a third contact means connecting said first slow-releasing relay means to an energizing circuit, said energizing circuit comprising further contact means, controlled by said impulsing relay and by said first and second slow-releasing relay means.

13. A system according to claim 5, wherein said impulsing relay operates a contact arrangement to connect said first slow-releasing relay means to an energizing circuit and simultaneously to disconnect said energizing circuit from at least one of said second and third slow-releasing relay means, while said distributor means is in its home position, said first slow-releasing relay means connected to control contacts for said second and said additional slow-releasing relay means to alternative energizing circuits while said distributor means is in one of said sub-station selecting positions.

14. A system according to claim 8, in which said distributor means is controlled by an energizing circuit operated by said relay means for controlling the switch when said relay means is energized and by said first slow-releasing relay means when de-energized.

EDWARD ALBERT HENRY BOWSHER. 

